It has long been known that propeller blades for driving a vehicle through a fluid should have a low pitch for providing maximum force to the vehicle for acceleration. At high vehicle speeds, however, the blade pitch should be increased to reduce engine r.p.m. while maintaining vehicle speed. It is also known to adjust propeller blades for the purpose of slowing, stopping, or reversing the motion of the vehicle. Further, it is common practice to use some sort of mechanism for positively driving the blades from a high pitch forward position toward the second end position of the blades, e.g. a high pitch reverse position, and then return the blades to their high pitch forward position by means of energy stored in a compression spring.
In the known systems of this type, one end of the spring is held against a stationary abutment and the second end of the spring is moved to compress the spring as the propeller blades are rotated by a a positive drive mechanism. Each increment of blade rotation causes an increment of compression of the spring attended by a storage in the spring of an increment force dependent on the design and size of the spring.
It is also known that most variable pitch propellers for aircraft and marine vehicles are relatively complex and expensive.
Examples of variable pitch propeller mechanisms found in a search of the patent literature are disclosed in the following patents:
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These patents and the prior art that is discussed and/or cited therein may be carefully studied for the purpose of putting the present invention into proper perspective relative to the prior art.